Air lift drier



P 0, 1966 F. E. JOHNSON ETAL 3,273,257

AIR LIFT DRIER 5 Sheets-Sheet 1 Filed July 9, 1963 7710/745 1f? ZEW/S.

IN VENTORS.

p 20, 1966 F. E. JOHNSON ETAL 3,273,257

AIR LIFT DRIER 5 Sheets-Sheet 2 Filed July 9, 1963 IKE-4' JE'IEHZE- a A m/ 745 E. [El W5. INVENTOR5,

p 1966 F. E. JOHNSON ETAL 3,273,257

AIR LIFT DRIER 5 Sheets-Sheet 3 Filed July 9, 1963 E T 6770/8 IVEXS,

United States Patent 3,273,257 AIR LIFT DRIER Frank E. Johnson and Thomas E. Lewis, Anaheim, Calif., assignors to Rietz Manufacturing (10., Santa Rosa, Calif., a corporation of California Filed July 9, 1963, Ser. No. 293,795 3 Claims. (Cl. 34-57) This invention relates generally to driers of the type in which drying air or other gas serves to lift the material being dried through a drying chamber.

There are many industrial applications where it is desired to flash dry moist materials having such physical properties that they cannot be handled by ordinary spray drying equipment. For example, reference can be made to such materials as moist fish meal, wood pulp, peat moss or woody materials that have been ground or shredded by milling. Air lift driers which have been used in the past have been subject to certain disadvantages. Particularly, the thermal efficiency obtained has not been as high as is desired. We attribute this primarily to inlet air temperature limitations and to the manner in which the particles :are subjected to the drying air during their passage through the equipment. Also, the equipment as previously constructed has not been subject to adjustment to effect optimum operation for different materials and different moisture contents.

In the general, it is an object of the present invention to provide improved drying equipment of the air lift type.

Another object of the invention is to provide equipment of the above character which will provide relatively good thermal efiiciency, and which will permit use of relatively high inlet air temperatures without causing burning or scorching.

Another object of the invention is to provide apparatus of the above character which is subject to control and adjustment whereby it can be adapted for optimum operation to suit various materials and moisture contents.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

FIGURE 1 is a side elevational view schematically illustrating equipment incorporating the present invention;

FIGURE 2 is a plan view of the equipment shown in FIGURE 1;

FIGURE 3 is a side elevational view in section illustrating the main drying chamber;

FIGURE 4 is a cross-sectional view taken as indicated by the line 4-4 of FIGURE 3;

FIGURE 5 is an enlarged detail in section taken as indicated by the lines 55 of FIGURE 3;

Referring to FIGURES 1 and 2, the equipment illustrated consists generally of a drying chamber or tower connected at its lower end to the inlet conduit 11, and

at its upper end to the discharge conduit 12. The discharge conduit is connected by the pipe or conduit 13 to the pneumatic separator or collector 14 of the cyclone type. During operation upward flow of drying air is maintained through the chamber 10, either by applying forced draft to the inlet conduit 11, or suction to the discharge conduit 12. Suction or induced flow is shown in FIGURE 1, in that the blower 16 has its suction side connected by conduit 17 to the exhaust side of the cyclone separator 14.

A furnace 15 is shown for supplying hot drying gas to the inlet conduit 11. In some instances, this furnace may consist of a fuel burner, with the gaseous products 3"273,z57 Patented Sept. 20, 1966 of combustion together with some atmospheric air constituting the drying gas. In other instances, atmospheric air or other gas may be heated to the desired temperature by contact with heated surfaces, before its delivery into the conduit 11.

A fee-d hopper 18 is shown for receiving the material to be dried. This hopper delivers the material to the housing 19a of a feed screw, and serves to deliver the material through the mill 20 to the feed conduit 21. The latter connects with the inlet conduit 11.

The mill 20 may be what is commonly referred to as a fluifer or some suitable form of attrition mill which will serve to break up caked or packed material into fragments of such size that they can be entrained in and carried upwardly through conduit 11 by the drying air. Where the material being supp-lied to the equipment is sufliciently free-flowing, the mill 20 may be omitted.

The lower end of the cyclone separator 14 is shown connected to the feed screw housing 19b, whereby collected material is delivered to the discharge conduit 22. Some form of suitable valve 23 can be interposed at the lower end of the cyclone separator, to regulate the discharge of dried material. The feed screws within the housing 19a, 1% may be on a single shaft with oppositely disposed flights, whereby in housing 19a the material is fed to the mill 20, and in housing 1% it is fed to the discharge conduit 22. In certain processing operations it may be desirable to continuously return a part of the dried material back into the conduit 18. A belt and pulley or other suitable drive 24 is shown connecting the feed screw shaft in housings 19a, 1% with the mill 20. Also a drive belt connection 26 has been shown for driving the feed screw shaft.

FIGURE 3 illustrates the construction of the drying chamber 10 and the parts associated with the same. In this instance, the chamber consists of three drying sections 10a, 10b, and 100. Between the sections 10a and 10b and serving to connect the same, there is a throat section 31a. A similar throat section 31b connects the drying sections 10b and 100.

The lower drying section 10a is shown comprising the frustoconical wall portion 33. Sections 10b and 10c are for-med by the substantially cylindrical wall portions 34 and 35. The throat section 31 is formed by the oppositely sloped frustoconical wall portions 31a and 31b, together with the interconnecting portion 310, which can be substantially cylindrical. Throat section 32 is similarly formed by frustoconical portions 32a and 32b and the substantially cylindrical connecting portion 32c.

As will be evident in FIGURE 3, the throat sections are somewhat venturi shaped in that they constrict and then expand with respect to cross-section flow area.

Located within the throat sections 31 and 32 there are the flow control bodies 36 and 37. Body 36 is for-med of connected frustoconical portions 36a and 36b, and body 37 is formed of similar portions 37a and 37!).

Both of the bodies 36 and 37 are mounted upon the vertical member 38, which can be in the form of a rod or pipe. This member extends slidably through the collar 39 of the spider 40, and at its lower end it is slidably disposed within the pipe 41. This pipe in turn is carried by the supporting spider 42.

A threaded pipe 43 is secured to the lower end of the pipe 38, and its lower portion, which may extend below the pipe 38, is enclosed by the tapered shroud 44. A shaft 46 is journalled in the pipe 41, and extends to the exterior through one side of the lower drying section 33, where it is provided with an operating crank 47. Miter gear shafts 48 and 49 operatively connect the shaft 46 with a nut 51, which engages the threads of rod 43. This nut is rotatively seated upon the wall 52 that is mounted upon the lower end of pipe 41.

Extending radially from the pipe 41, I provide vertically extending vanes 53 which tend to prevent swirling action of the drying air in this region of the chamber.

It will be evident that by manually turning the crank 47, the member 38 together with the bodies 36 and 37 can be raised or lowered to a desired position. As shown in FIGURE 3, both bodies have their portions of maximum diameter located within the portions 310 and 320 of the throat sections 31 and 32. Flow upwardly through the chamber is confined in the throat sections to the annular orifices '56 and 57. When both of the bodies 36 and 37 are raised, for example to the positions illustrated in dotted lines, the orifices 56 and 57 are effectively increased in cross-sectional flow area. Thus, by operating the crank 47, the operator may set the equipment for optimum drying'of particular materials.

Operation of the equipment is as follows. It will be presumed that the equipment is being operated to dry fish meal.

The moist fish meal is fed into the hopper 18 and as it passes through the fluifer'20, individual fragments are broken apart so that the material as it drops through the conduit 29 has such physical characteristics that it is entrained in and elevated by the upwardly moving stream of drying air. An upward draft of drying air is maintained continuously through the drying chamber or tower by operation of the blower 16. By way of example, the temperature of the air passing through the conduit 11 may be of the order of from 250 to 350 F. or higher. The successive sections 10a, 10b and 100 in effect form drying. stages through which the material progressively passes.- In the lower section 10a, the crosssectional flow area increases gradually due to the shaping of the truncated wall portion 33. The flow rate through ,the inlet conduit 10 should be maintained so that none of the material can drop back into this conduit. In the upper part of the section 10a, there may be some dropping back of material which is relatively heavy because of its moisture content. As the material progresses to the upper part of section 10a and into the lower part of the throat 31, the surrounding air is subjected to increasing flow velocity which serves to accelerate upward movement of the material and to carry it through the annular orifice 56. Immediately above the orifice 56, the upward flow of drying air decreases in velocity, and likewise there is a deceleration of upward movement of the particles. In the upper portion of the section 10b, there is likewise some dropping back of material due to its moisture content. Here again, however, the drying air passes into the lower portion 32a of the throat section 32 and increases its upward flow velocity and thus carries the material being dried through the annular orifice 57 into the upper section 10c. In the upper section 100, the drying continues to substantial completion. Here again there is some continual dropping back of incompletely dried material whereby as the material passes outwardly through the conduit 12, it is relatively uniform with respect to attainment of the desired moisture content. There is no dropping back of material from the conduit 12 because of the relatively high flow velocity maintained.

It will be evident from the foregoing that my construction serves in effect to divide the drying effect into three vertically spaced sections or stages. In general, the material has its moisture content reduced to a certain amount in the lowermost section 10a, and then the material passes abruptly to the next section 1012. Here there is some further reduction in moisture content, after which the material passes rapidly into the uppermost section 100, where the moisture content is reduced to the desired value. By virtue of the various stages or sections, there is substantially no opportunity for material upon its introduction being delivered to the outlet 12. Also, the dropping back action previously described is confined to each individual section. In other words, material will not drop back from the uppermost section 10c into the section 1017, nor from the section 10b into the lowermost section 10a.

A further advantage of my construction is that it permits maintenance of a substantial temperature diiferential between the various sections. In other words, in the first section 10a the drying temperature is at a-maximum, whereas successively lower temperatures are maintained in the sections 10b and 100. Generally, a higher temperature can be tolerated in the lower section 10a, be cause in this section the material has its greatest moisture content. It will be evident that this maintenance of a desired temperature gradient is also assurance against contact of the high temperature gas with dried material and makes for elimination of undesired scorching or burning.

In the drying of materials having dilferent physical characteristics, it may be desirable to adjust the temperature of the inlet dry air. In general, this temperature should be maintained as high as is possible with the material being dried. Also, in the drying of different materials, the bodies 36 and 37 can be adjusted to vary the flow velocities through the orifices 56 and 57. Particularly with materials which are relatively wet or comparatively heavy, it will be found that the higher velocities through the orifices 56 and 57 are desirable. Conversely, where the material is readily suspended, that is, relatively light in weight, the flow velocities through the orifices 56 and 57 may be reduced by their enlargement.

We claim:

1. In a drier, an upright drying chamber or tower formed to provide at least two drying sections, one being disposed above the other, a throat section connecting the drying sections, the throat section being stormed by oppositely sloped aligned frust-oconical walls and a substantially cylindrical portion connecting said walls, the lower end of the lowermost section being adapted to receive material to be dried together with a stream of drying gas, .a discharge conduit connected with the uppermost end of the upper section for discharge of drying air and dried material, and means disposed within said throat section for adjusting the cross-sectional flow area through the same, said means comprising a body formed substantially of two connected frustoconical walls whereby said body is tapered toward both its ends, the greatest diameter of said body being less than the diameter of the substantially cylindrical portion, said body being disposed axially within the substantially cylindrical portion of said throat section thereby providing together with said throat section an annular orifice through which the drying gas and material is caused to pass.

2. Apparatus as in claim 1 in which said body is vertically adjustable.

3. In an air drier, an upright drying chamber formed to provide at least three vertically spaced drying sections, all of said sections being circular in cross-section, said drying sections being connected by throat sections, each of said throat sections being formed of frustoconical walls that are oppositely sloped whereby each throat section is divergent toward its upper and lower extremities together with a substantially cylindrical portion that connects said trustoconical walls, and means for controlling and adjusting the flow of drying gas and material being dried through each of said throat sections, said means comprising a body located axially within the substantially cylindrical portion of each throat section, each body being circular in horizontal cross-section and being tapered to a reduced diameter toward both its upper and lower ends, the largest diameter of each body being less than the diameter of the corresponding cylindrical portion, a single vertically extending member upon which said bodies are mounted, and means for vertically a-djusting the position of said member and the location of 5 6 said bodies thereby to vary the annular cross-sectional 2,890,764 6/1959 Arnold 34-57 X flow area of the annular orifices provided about each of 3,178,830 4/1965 Mark 34-57 the FOREIGN PATENTS References Cited by the Examiner 5 463,060 3/1937 Great Britain.

UNITED STATES PATENTS FREDERICK L. MATTESON, 111., Primary Examiner. 2,513,370 7/1950 Shaw 3457 JOHN] CAMBY Examiner 2,607,537 8/1952 Shaw 241-47 

1. IN A DRIER, AN UPRIGHT DRYING CHAMBER OR TOWER FORMED TO PROVIDE AT LEAST TWO DRYING SECTIONS, ONE BEING DISPOSED ABOVE THE OTHER, A THROAT SECTION CONNECTING THE DRYING SECTIONS, THE THROAT SECTION BEING FORMED BY OPPOSITELY SLOPED ALIGNED FRUSTOCONICAL WALLS AND A SUBSTANTIALLY CYLINDRICAL PORTION CONNECTING SAID WALLS, THE LOWER END OF THE LOWERMOST SECTION BEING ADAPTED TO RECEIVE MATERIAL TO BE DRIED TOGETHER WITH A STREAM OF DRYING GAS, A DISCHARGE CONDUIT CONNECTED WITH THE UPPERMOST END OF THE UPPER SECTION FOR DISCHARGE OF DRYING AIR AND DRIED MATERIAL, AND MEANS DISPOSED WITHIN SAID THROAT SECTION FOR ADJUSTING THE CROSS-SECTIONAL FLOW AREA THROUGH THE SAME, SAID MEANS COMPRISING A BODY FORMED SUBSTANTIALLY OF TWO CONNECTED FRUSTOCONICAL WALLS WHEREBY SAID BODY IS TAPERED TOWARD BOTH ITS ENDS, THE GREATEST DIAM- 